


above the salt

by flowerpetal275



Category: Shingeki no Kyojin | Attack on Titan
Genre: Adult Eren Yeager, Alternate Universe - Fantasy, Badass Levi Ackerman, Character's Name Spelled as Hanji, Cultural Differences, Cute Eren Yeager, Emotional Hurt/Comfort, Eren Yeager Is a Ray of Sunshine, Eren Yeager is a Little Shit, Ereri AU, Hange Zoë's Experiments, Hurt/Comfort, Language Barrier, Levi Ackerman is Bad at Feelings, Levi Ackerman is in Denial, Little Mermaid Elements, M/M, Magical Tattoos, Mermaid Eren Yeager, Merperson Eren Yeager, No Smut, Nonbinary Hange Zoë, Pirate Levi Ackerman, Prince Eren Yeager, Prince Levi Ackerman, Romance, Sea Monsters, Strangers to Lovers, ereri, mermaid au
Language: English
Status: In-Progress
Published: 2021-03-11
Updated: 2021-03-10
Packaged: 2021-03-16 07:28:06
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 7,527
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29946543
Author URL: https://archiveofourown.org/users/flowerpetal275/pseuds/flowerpetal275
Summary: Levi Ackerman, prince to the kingdom of Maria, finds himself washed ashore. The last thing he remembers is his ship crashing...so how had he gotten here?His question feels shit-stupid as he stares up at a pair of glistening, teal eyes. "What in the hell?" He murmurs, scrambling away from the boy lying atop him.Confusion collides with fear as Levi notices the multicolored tail attached to the boy at his waist.Ah, fuck. As if Levi's life couldn't get any crazier.~OR~levi/eren mermaid au!
Relationships: Levi Ackerman & Eren Yeager, Levi Ackerman/Eren Yeager
Comments: 6
Kudos: 7





	1. a rising tide lifts all boats

**Author's Note:**

> ahhhh i've never written one of these before, but i've always wanted to! 
> 
> let's see how this goes!

For as long as he could remember, Eren Yeager had a constant admiration for the life that existed beyond the crashing waves of the ocean. The land called to him, his curiosity continuously overcoming his deep-rooted fear for the human race. 

Growing up, it'd been instilled within Eren to hold a constant fear for the land-dwellers above the surface. 

They'd experiment on the Merpeople, kill them, eat them---at least, that's what his father always told him. His father, King Grisha, ruled the seven seas. And by the gods, he ruled them with an iron fist. 

Ever since Eren’s mother died at the boy’s tender age of thirteen, his father had held this overprotective umbrella over Eren, guarding him against any and all possible danger the seven seas had to offer. Unfortunately, the lockdown his father had on him only drove Eren's curiosity for the unknown further above the ocean's tide. 

His beautiful cerulean eyes scan the sandy shore, searching for anything he might be able to sneak up and snatch. Eren loved snatching knick-knacks from the sand, it gave him a rush of adrenaline and he got to take the trinket back to his secret little cove beside the local coral reef. 

A spike of panic shoots through him as he notices a human sitting on the shore, staring out at the waters. Eren dips his head down, so the water is leveled at the space between his eyes and nose. The human doesn't seem to notice him, thank the gods. 

__

Levi Ackerman, prince to the kingdom of Maria, sits upon the warm sand, his toes buried in the grain. The breeze blows softly against his skin, bringing an air of peace to his typically rigid attitude. 

With a sigh, he sets the small music box he'd been working on down, deciding to take a break from tinkering on it. 

The damned thing broke the other day, and, while he'd never admit it, Levi missed the tune it used to sing to him. It was what his mother always hummed to get him to sleep, but she'd passed away when Levi was little. 

Since she died, he'd never slept well without hearing it before bed. He knows how childish it sounds, but it was nothing he could help. The last few nights had been hell due to the music box being out of commission. 

Levi was not someone to ask for help, especially for something as childish as a music box. He was twenty-two for fuck's sake, not five. 

Maybe he should head back inside. It was getting to be sunset and he knew Hanji would be looking for him. Hanji always seemed to be looking for him, it was like the mad-scientist never left him alone. 

He stands, dusting the sand off his pants and walking back to the small rock wall behind him to grab his shoes. 

God, Levi really wished he could just stay here forever. The ocean always had this unbothered nature about it. The tide never cared how it went in or out, the fish swam freely among the depths. There was no rule, only unfettered existence. This is what Levi longed for, it's what he's always longed for. 

Just as he starts climbing the small path back up to his castle that sat upon the ocean-side, he remembers the music box he'd left on the shore. Damn it. 

Turning back, his eyes go wide as he realizes it's nowhere in sight. The only significant manner in the sand is the odd two-foot-wide streak of sand dragging right to where his music box had been, then right back out to the sea. 

How in the ever-loving fuck had that gotten there? 

The music box was, quite unfortunately, nowhere to be found. "Goddamnit." Levi curses, rolling his eyes as he flips around and heads back up to the castle. 

The damned thing was probably dragged out to sea by the tide or something, never to be found again. 

What the hell was he supposed to do now? 

__

Eren fiddles with the small square of wonder, mildly out of breath due to the effort of dragging himself on and off shore as fast as he had. 

Getting caught in the sand always terrified Eren, the mental image of being beached and dying of dehydration sending shivers up his spine. 

Now---what was the little machine supposed to do? 

He was currently hiding behind a rock, trying to keep the trinket from hitting the water. He'd noticed that oftentimes when that happened, a weird, red material grew on it. It was scratchy and uncomfortable to touch. 

With one hand holding the box above the salty sea, Eren swims to his small, hidden cove that resided a little ways away from the shore beside the castle. 

He sits on a rock inside the secluded cove, fiddling with the object. There seemed to be a latch on it, one Eren quickly made sense of. 

Inside, different metal pieces and small tools lay rustling around. Awesome! Eren was always crafty, it was one of his specific talents. 

It takes a little over ten minutes to fix the box, but it was time he was more than willing to spend to understand more of humankind. 

There's a small lever in the back, and Eren gives it a good turn before setting it back down. Music starts emanating from the device, initially startling Eren. By the first note, Eren's already halfway across the cavern, hiding behind a rock. 

The box plays a tune, one unfamiliar to Eren's keen ears. However, Eren catches on fast, singing along with the melody and even harmonizing with it on a few notes. It was a beautiful composition and Eren quickly found it stuck in his head. 

The Merpeople loved music. It was a key element of their culture. 

However, they were never the kind to compose new songs, always sticking to what they knew already. Instruments didn't really work well underwater, so they were only able to use their voices for choirs and such. 

The lack of equipment to write new jingles is what lead to them remaining confined to only the songs they could pass down from generation to generation. 

So, hearing this new piece was rather enchanting for the young mermaid. 

And well, that's basically how he spent his entire day---sitting in his secluded cove, humming along to the tune for hours on end. 

His mind wanders to the human he'd seen sitting in the sand. In the moment, he hadn't had the time to admire his features, but now, Eren was happy to think back on his mesmerizingly charming qualities. 

His jawline was sharp, eyes dark and stern. His hair fell forward over his face, but just enough so Eren could still see his glistening, stormy grey eyes. T

The image was something Eren both could not and would not let stray from his mind. He was now bound and determined to see him again, if only to watch from afar. 

The man was simply too captivating to let slip away that easily.


	2. a hewer of wood and a drawer of water

**Summary for the Chapter:**

> a stolen glance of the other side.

Okay, Levi was officially done with this shit. He couldn't find the stupid ass music box anywhere, and no one else knew the tune. 

The melody was something Levi kept hidden, knowing it was the last piece of his mother he had left. She'd composed it and built the music box herself, so it had never really reached anyone's ears but Levi's. 

Sure, Levi knew the notes like the back of his hand, but he couldn't sing for shit. He knew he could recognize the notes as soon as he heard them, but actually making the noises felt close to impossible. 

All in all, his situation was hopeless. Fucking phenomenal. 

With a sigh, he plops down on the sand again. This place seemed to be his only remaining peace in his world of responsibility. Levi was to inherit the throne after Erwin passed, but that wouldn't be for a while. 

Still, Levi constantly felt like he had to deal with everyone's shit. He needed a break. 

Laying back against the soft beach, he shuts his eyes and takes a few breaths. The delicate sound of the waves dancing across the shore lulls him away into a dreamless sleep. 

__

Now was his chance! 

Darting as fast as he can through the water, Eren grabs the mysterious box from his cove and swims back to the shore where the man lay. 

He could give the music box back, now that he'd fixed it. 

But sneaking past a human? The thought terrified Eren. What if he woke up? What if Eren couldn't drag himself back to the water in time? So many risks. 

The fear gave him all the more motivation to do it. 

With as much strength as he can manage, Eren thrusts himself out of the water and up the shoreline. The dry sand tickles his fin, sending shivers down his spine. 

Using his forearms to dig into the mushy ground, he wiggles his way all the way up to the human and sets the box down. Victory! 

Now, to escape with his life. 

He shuffles down the small slope, sighing in relief as water graces his arms. 

Panic shoots through him again as he hears the human stir behind him. He was waking up! 

__

Levi sits up, rubbing at his eyes. Damn, short nap. 

His eyes widen in slight disbelief just as he sees a huge fin slap into the water, disappearing into the darkness of the ocean. What the hell was that? 

He'd never seen a fish with that color scales before, or a tail angled horizontally like that. Maybe a dolphin? 

But why would a dolphin be that far on shore? 

Every question he'd had is put on the backburner as he finds the music box sitting next to him. 

"The fuck?" He curses quietly, fiddling with it. He turns the lever in the back, gasping lightly in surprise when he hears it gently playing out the familiar melody. 

The same streak of sand as before leads all the way up beside him, then back to the water. Something had definitely crawled up here. But what? And how had Levi not woken up when it got near? 

Nothing made any sense. 

Everything made even less sense when he made eye contact with a head peeking out from the water only ten feet or so past the shore. 

"Hello?" He calls out, utterly confused. He didn't think anyone was swimming here, or ever even came to the castle's beach? 

The brunette boy, looking rather young, had beautiful teal eyes, ones that almost mesmerized Levi. No, they _did_ mesmerise him. They were gorgeous, nothing like anything he'd ever witnessed before. 

Who was the mystery boy? 

Had he been the one to fix his music box? How? 

__

Boy, oh boy, was Eren excited to learn the man knew English. Eren was fluent in many languages, English being one of them. 

However, his fear easily overcame his crave for knowledge. "How did you fix it?" The guy holds up his magical square of music. 

Should he say something? It’s not like it could hurt anything, could it? 

"What's your name?" The human asks. 

Well, Eren could at least answer that. It's not like he could get to him this far in the water anyways. "Eren." He murmurs out, blinking. 

The human seems pleased to have finally gotten an answer. "Levi." He replies. 

Levi? Interesting name. Eren hadn't heard it before. "Levi?" Eren echoes, eyebrows bunched in thought. 

__

Levi hesitates. Isn't that what he'd just said? "Yeah...?" There's a pause as the two watch each other curiously, "Why don't you come over here?" 

He sees Eren tense up at the request. The boy shakes his head. "Why not?" Levi asks, the slight curiosity in his voice only growing. 

However, Levi never does get his answer. 

"Leviiiii!" Hanji calls from atop the pathway to the beach, their voice echoing. "Where did you go?" 

Turning around to give Hanji the stink eye, he replies, "Oh, for fuck's sake, Shitty Glasses---can't I have two seconds alone for once?" 

"Nope. You'll get lonely in one." They bounce down the sand, hopping from foot to foot playfully. "I have some questions!" 

"Can't you see I'm busy?" Levi gestures a hand behind him, towards the sea. 

Hanji hesitates, "With what?" 

Levi turns back around, "Him!" His eyes widen a bit as he realizes the boy that once bobbed lightly in the water is now gone. 

What the hell? 

He hadn't climbed back to shore and left, that was for sure. Both him and Hanji would have seen him leave. 

Did he go underwater? Was he drowning? 

No, Levi would've heard the commotion if the boy was drowning. 

All in all, Levi was mind-fucked. Where'd Eren go?


	3. abandon ship

**Summary for the Chapter:**

> a rescue, a friend.

It'd been about a week since Levi had last seen Eren on that shoreline. He never knew where the boy went, or if he was okay. 

Each day that passed brought more concern to Levi's thoughts. 

And, naturally, Levi's change of mood didn't go unnoticed by his castle's physician, Hanji Zoe. "Still thinking about Eren?" 

He looks to Hanji sitting beside him, eyes stern. He'd told them about Eren, and Hanji seemed to be just as curious about Eren as Levi himself was. "He's probably dead." Levi deadpans. 

The prince was preparing himself for the worst. He hoped to god that the boy wasn't deceased, but he needed to be ready in the case that he was. "Oh, you don't really believe that!" Hanji laughs, slapping Levi on the shoulder. "I'm sure he'll turn up again sooner or later, wherever he lives. Probably somewhere along the shoreline." 

The man gives a small nod of agreement, continuing his trek to the ship floating gracefully in the water beside the dock. 

They were about to go on a three-day-long fishing expedition to gather resources for their kingdom. Hopefully, they'd come back with enough fish to feed the local village for at least a month. 

Erwin sent Levi on this quest specifically, since he didn't trust any of his other commanders to get the job done the way he wanted. 

"I'll see you in a few days!" Hanji cheers from the deck, waving their hand wildly at Levi. 

Levi rolls his eyes, annoyed by his friend's boisterous attitude. His aggravated response doesn't deter Hanji's upbeat demeanor in the slightest. 

__

Eren follows the ship curiously for the next day and a half. His father typically didn't care what Eren did, so long as he was safe and within eye-shot of either him, Mikasa, or Armin. 

Somehow, Eren had managed to convince his father he was going to hang out with Mikasa. He'd also convinced Mikasa he was hanging out with Armin. Aaand he'd convinced Armin that he was spending the day with his father. 

So long as their paths didn't intersect, they all believed Eren was spending his time with a different one of the three. So far, it was working out great. 

A storm raged on above the surface, the loud thunder only lumbering slightly beneath the waves. Eren was, to say the least, worried for his friend on the ship. 

He'd seen many ships on the bottom of the ocean littered with dead bodies, slowly being devoured by numerous different kinds of sea life. 

Eren would hate to see Levi add to that devastating list of casualties. 

And by the looks of it, he just might. 

A loud crash is heard from above Eren, startling him out of his thoughts. Large, weird billows of red suddenly erupt into the darkness of the ship. 

What in the world was that?! It was nothing Eren had ever seen before. 

Bodies start to drop into the water, surprising him. He sinks a bit deeper into the pitch-black shadows of the ocean, trying to keep out of sight just in case. 

That's when Eren sees him. 

"Levi!" Eren cheers, adding a few clicks of excitement afterward. His friend had joined him in the water! 

While he remained terrified of the human race, he'd found Levi to be an odd exception. He didn't understand why, but Levi didn't instill fear within the mermaid as every other human had before. 

Yeah, he’d only met Levi once, but during that time, Levi had been nothing but curious to Eren, nothing like the ruthless killers he’d been raised to perceive. 

Eren quickly realizes Levi wasn't swimming. Why wasn't he swimming? 

Was he okay? Should Eren take the risk of getting any closer? 

He didn't seem to be conscious, so it's not like he'd see Eren anyways. 

Taking a tentative glide forward, he wraps an arm around Levi. "Levi?" He asks again. After no reply, Eren gives a bit of concerned chittering. He wasn't okay? 

A bit of blood seeps into the water, and immediately, Eren became terrified. As a royal prince of the ocean, he'd never feared sharks. But he also knew when a shark smelled blood, they reverted to their animalistic instincts, royalty set aside. 

Both his and Levi's life was now in danger. Not to mention, Levi didn't seem to be breathing. 

As fast as he can manage with a bleeding human at his side, Eren rockets through the ocean at speeds he didn't even know he could travel. It takes maybe two minutes to get back to the closest shore, the shore at the castle. 

Eren drags Levi up the seabed and onto the beach, grunting with effort. He was exhausted at having to travel so far, and at such an unimaginable pace. 

He pulls him up a bit farther, worried if he left him here, Levi'd get washed away by the tide when it came up. 

Once they were far enough away from the shoreline, Eren huffs with disbelief. 

Did he seriously just save a human? 

Wait, not save---he still wasn't breathing. What does he do?! He doesn't know how human anatomy works! 

Well, one thing Eren does know is they aren't supposed to be bleeding like this. There's a large chunk of flesh missing from Levi's shoulder, the wound gushing blood out onto the sand. A trail of the crimson color leads back out into the ocean. 

"Uh, okay, uh-" Eren stutters, thinking that maybe Levi would reply if he spoke to him, "I'm gonna help? Okay?" 

No response. 

With a huff, Eren places two hands on Levi's wounded shoulder, laying his fingers atop each other with his thumbs crossing to create a small circle with the spaces between his thumbs and forefingers. 

Shutting his eyes, Eren hums a small healing hymn and feels the colorful tattoos lining his arms glow with power. The tattoos connected at the back of Eren's neck, at the nape. 

The nape had always been a cherished element of a mermaid's body. It's where they stored their power. 

Merpeople would bejewel it, tattoo it, anything to give it significance. It truly was a gift given to them by Amphitrite, goddess of the sea. 

After a few minutes of the enchanting poem, Eren opens his eyes to find the wound completely healed. Perfect! 

Levi coughs up a mouthful of water, then falls right back into unconsciousness, breathing evenly this time. 

A sense of relief floods through the mermaid. However, Eren's energy source seemed to be completely depleted. His arms buckle out from under him and he collapses on Levi's chest. 

No, no, no---he can't pass out here. He's on land! The sun will be up soon, and Eren could only picture himself dying of dehydration here on the sand. The prospect horrified him. 

Not to mention, he was laying on top of a human. Oh, this was a mess. 

Eren grips the small key necklace he has looped around his neck, searching for some sense of comfort from it. 

His mother had given him the jewelry right before she died, telling him to be sure he never lost it. 'It's your only opportunity to know more, to know everything I never got the time to teach you', she'd tell him. 

Eren never knew what it meant, he still didn't. But he knew he was never letting it go. 

Fortunately, Eren loses any more time to panic further as he's lulled away into the same unconsciousness that consumed his humanoid friend beneath him.


	4. where the ocean meets the sand

**Summary for the Chapter:**

> two worlds collide.

Levi stirs a bit, groaning. What the hell happened, and why the fuck did it feel like someone hit him with a cannonball? 

Something oddly light weighs down on his chest. Squinting his eyes open, he realizes he's laying face up outside. 

The familiar, salty scent of the ocean overcomes his senses. Was he on the beach? 

Sitting up, he looks around. 

The last thing he remembers is his ship crashing...so how had he gotten here?

His question feels shit-stupid as he stares up at a pair of glistening, teal eyes. "Eren?" He murmurs, bunching his eyebrows at the boy lying atop him.

Confusion collides with fear as Levi notices the multicolored tail attached to the boy at his waist.

Ah, fuck. As if Levi's life couldn't get any crazier. 

__

Eren feels something move beneath him. What happened again? His head feels like it's stuffed with seafoam. 

Terror flashes through him the second his eyes open. 

He was beached. Beside a human. Beside _Levi_. 

Aaaand now Levi was staring right back at him. 

They both scream, scrambling away from each other. "What the hell are you?!" Levi shouts, his face screwed up in slight horror. 

As fast as he can manage, Eren tries to squirm away, back to the water. The effort is futile, considering he was already dehydrated and the tide went in early in the morning. "Please!" Eren pleads, holding his hands out in front of himself for protection. He was helpless outside of the water. "Please, don't kill me!" 

__

Levi was completely, totally, and utterly mind-fucked. 

Yeah, he asked the creature what it was, but Levi very well already knew. He'd heard stories about mermaids when he was little, tales of humans with a fin for legs. 

However, it was always passed off as a myth. No one had ever seen one before, or had evidence of their existence. 

Eren lies there, shaking with fear. His skin looks red, probably sunburnt from sitting under the heat of the sun all morning. "Eren?" Levi murmurs, still trying to wrap his mind around the situation. 

Eren continues to panic, struggling and failing to pull himself back to the water. He really wasn't going anywhere. The boy was stuck, and they both knew it. 

"I'm not gonna hurt you." Levi soothes, crouching down beside Eren to try to calm him, "Okay?" 

Eren hesitates, a bit confused. "You're not?" No, Levi was never going to hurt Eren, but Levi had to admit the boy was too trusting for his own good. 

"No, of course not." Levi's eyes study the mermaid's face, then trail down to his tail. A beautiful array of blues and green scales cover his fin, glistening beneath the sun. 

He reaches a hand out to touch it, but flinches back when Eren gives a yelp of fear. "Sorry." Levi apologizes, grimacing. "Were you the one who saved me?" 

After a moment of hesitation, the mermaid nods. "Your boat crashed." He murmurs. 

Levi gives the smallest of smiles, finding the boy's sheepishness adorable. "Are you what I think you are?" 

Eren tilts his head at this, confused. "And what would that be?" 

Damn, did Levi feel stupid saying it out loud. So, he just moves onto the next question, "Are you hurt?" He'd noticed the mermaid's shaking hands and unfocused eyes a few moments prior. 

Eren only points to the sky, "The sun." He murmurs, throat dry. "I have to get to the water." 

"Does it dry you out?" Levi asks curiously. The mermaid nods. 

"Please, I don't wanna die here." Tears remain thick in Eren's voice, shattering Levi's heart. The boy just seemed so _scared_. 

"I'm not gonna let you die, don't worry." An overprotective nature overcomes the land-dwelling prince, the urge to care for the boy overcoming any of the looming fear he'd previously harbored in his thoughts. 

Letting the mermaid go was the last thing Levi wanted to do. He was worried he'd never see the boy again, never once more witness this myth come to life. Even more than that, Levi had very quickly developed a certain infatuation with the boy himself, regardless of his aquatic nature. 

However, he was also aware of how completely terrified Eren must be. Not to mention the fact that he was slowly dying out here in the hot sand. "Am I ever going to see you again?" Levi asks gingerly, looking from Eren to the water and back again. 

After a short moment, the mermaid prince nods, his dry, cracked lips turning up in a small smile. "Just please _help me_." He pleads with Levi. 

"Well then let's get you back in the water." Levi hums in thought, looping his hands under Eren's arms and dragging him backwards to the water. The mermaid was surprisingly _very_ light. 

" _Levi?!_ " Hanji's obnoxious, yet concerned voice calls down from the pathway entrance. 

"Fuck." 

__

Eren freezes, hearing the voice of another approaching human. Oh, gods, he was really in for it now. 

He knew he wouldn't be so lucky as to encounter _another_ kind human, not after Levi. What if this one wanted to eat him?! 

Eren squeals in panic, shifting in Levi's grip. "Please! I can't let them see me." 

Levi pulls Eren to the water quicker, surprised that the mermaid had managed to drag the both of them so far up the beach. 

That's right when the other human rounds the corner. "Levi! What the hell?! I thought you were at sea!" They gesture wildly at Levi, but freeze in their place when they see Eren. Yeah. They were totally about to eat him. 

"What in the-?!" Their voice catches in their throat as they take in the sight of Levi dragging a mermaid across the sand. "Levi, when were you gonna introduce me to your friend here?" 

"Damn it, Hanji!" Levi growls, gently laying Eren back down to stomp up to the physician. "Just walk away! No one needs to see this. Forget you were here!" 

"Pfft, as if!" They snort, lightly shoving past Levi to approach Eren. The mermaid squirms back, shrieking in fear. "Oh, honey, don't worry! I won't hurt you, I just want to get a good look at you." 

Their eyes study every one of Eren's features, from head to fin. "Leave him alone, shitty glasses!" Levi curses, grabbing their shoulder to tug them away. 

"Levi, do you know what this means?! All my research, it's not shit-worthless!" They cheer, bouncing up and down in excitement. "I told you! I _told_ you they were out there! And look at him! Oh, he's just gorgeous." 

They crouch down beside Eren again, gently moving to touch his tail, "Stay away!" Eren shoots out, trying to wiggle his way away from Hanji. 

"You're scaring him, shitty glasses." Levi rumbles, obviously aggravated by their awe-struck attitude. "Either get your ass out of here or help me get him back in the water." 

"Oh, no way!" Hanji gasps, standing to look Levi in the eye, "I need to study him!" 

"There is no way in fucking hell I'm letting you do your little experiments on Eren!" The prince shouts in their face. 

Hanji gasps lightly, " _This_ is Eren?!" They shriek, "So, he's coherent? Self-aware?" 

Levi facepalms. "Yeah, he's like a person, just with a fucking tail." 

"Then we have to help him! I can tell he's already severely dehydrated, no doubt from being out in the sun for this long. We can bring him back up to the castle and get him some help!" Hanji dances with excitement. 

"Please, I just wanna go home." Eren pleads, interrupting their conversation. 

Exhaustion clouds his thoughts, reminding him of the ailments of a mermaid's dehydration. In mere seconds, he's lost to the darkness yet again. 

"Eren!" Levi shouts just as Eren passes out.


	5. ahoy there

**Summary for the Chapter:**

> an excited hanji meets an apprehensive eren (: kind of?

"Eren!" Levi shouts, running up to the mermaid lying at their feet. "Eren, are you alright?" 

"He didn't die, did he?" Hanji shrieks, checking his pulse. They seem surprised, "His pulse is actually very fast." 

"Just shut your trap and help me get him up to the castle!" Levi growls out, moving to pick Eren up. His form is shaking lightly, drawing a breath of concern through Levi. 

He scoops the boy up, bridal-style. "Is he heavy? His tail has _got_ to be heavy, right?!" Hanji asks excitedly. 

Levi rolls his eyes, "Quit asking questions." As fast as he can manage with the constantly fluctuating sand beneath his feet, he carries Eren up to the castle, near the beach-front entrance. "How do we hide him?" 

"Uhhhh..." Hanji hums, thinking, "Wrap him in a tarp?" 

"Oh my god." Levi squeezes his eyes shut, aggravated. "Fine, find one." 

Hanji leaps away. Levi takes the moment to really study Eren this time, taking in his every little feature. He looks to be around 18, maybe 19. 

Intricate, yet somehow remarkably simple, golden tattoos trail up the outside of his arms from his wrists all the way up to the back of his neck. Two shimmering golden waves are tattooed onto his pecks, symmetrical and satisfying to the eye. 

A silver key hangs from a string on his neck, almost like a necklace. Levi wonders what the key goes to. 

Even while unconscious, Eren looks oddly flawless. The way his chocolate brown hair flows forward, head lulling against Levi's chest, gives a charming aura to the boy. If only those gorgeous eyes would open, so Levi could enjoy the full image of pure, natural beauty. 

Maybe someday. 

Hanji comes bouncing out from around the corner, holding a large, grey leather tarp up. "I found one!" 

"Fucking finally." Levi sighs, stressed. 

Hanji lays the tarp out, carefully helping Levi set Eren down on top. They lift the corners up to cover the mermaid's tail and upper body. "There we go! So, where we takin' him?" 

Levi thinks for a moment. "My bathroom, we can put him in the bathtub. We can't let anyone else know about him." 

"Oh, this is so exciting!" Hanji hurrahs, clapping their hands together. They hold the door open, Levi carrying Eren through and down the hall. "It's like a secret mission!" 

"What secret mission?" The two tense at the new voice. Slowly turning around, they come face to face with one Jean Kirstein. "Whatcha got there, Levi?" 

"Back off, dickwad." Levi curses, not in the mood for Jean's shit at the moment. Jean wasn't an asshat, he was just annoying as fuck. Then again, so was everyone else. 

"Ooooh, nothing!" Hanji smiles, wrapping an arm around Jean to pull him away, "Say, I was wondering if you could help me with something!" 

They pull Jean further down the hall, turning to give Levi a look that says, "Move it!" 

Without a second of hesitation, Levi starts bustling to his private quarters. He closes the door with his foot, sighing in relief. "You're safe, Eren." He whispers to the aquatic boy in his arms, wrapped firmly in the tarp. His skin is pale, tight with dehydration. 

Levi hurries into the bathroom and immediately starts running the bath, being sure it's at room temperature since he isn't sure how Eren would react to specifically hot or cold water. Shutting the faucet off, he gently lays Eren in the bath. 

He brushes some of the hair away from Eren's eyes, hoping this is how he's supposed to hydrate him. "Please be okay." Levi pleads quietly, glad no one else is around to witness his brief moment of emotional vulnerability. 

He doesn't have many. 

Thankfully, almost all of Eren's body is able to fit inside the tub, besides his head. Levi was sure Eren would get too cramped before long, but it'd have to do for now while he and Hanji took care of him. 

Levi grabs a glass of water, figuring forcing Eren's unconscious body to drink some water might help him a bit. Do mermaids even drink water? 

Tipping Eren's head back, Levi drizzles some water into his mouth. He watches with relief as Eren swallows reflexively. 

Levi's fingers graze Eren's neck, his eyes catching sight of weird tattoos there, too. Wait---were those gills? 

They seemed to be decorated with the same simple, beautiful golden tattoos covering his arms and upper body. 

I guess it made sense that Eren had gills, he was part fish after all. Was that rude to say? Levi had no idea how mermaid culture worked. 

He spends the next five minutes doing the same thing, giving Eren small bits of water in regulation. Maybe he's hungry? 

What the hell is he supposed to feed a mermaid?! They have to eat fish, right? What else would there be to eat in the ocean? 

The bathroom door slams open, revealing a panting Hanji. "I lost him! Finally!" They laugh breathlessly. 

"The hell did you do with Jean?" Levi sighs. 

"Just sent him on a little job, don't worry." They wave the prince off, kneeling down beside the bathtub with him. "But don't be surprised if half the forest is on fire by nightfall." 

"Hanji!" The man seethes angrily, eyebrows raised. 

"I'm kidding, I'm kidding!" However, the glance they give afterwards convinces Levi they're not. "So how's our little goldish doing?" 

"He's not a goldfish, and I have no idea." He replies, deadpan. "I managed to get some water in him, but I don't even know what he eats." 

"Fish makes the most sense?" Hanji shrugs, gently brushing their fingers against the tattoos on Eren's arms, eyes wide in awe. 

"That's what I thought." Levi ponders on it for a moment, unsure of how to help his new friend, "We should wait to get anything till he wakes up." 

"God, I still can't believe this! I knew they were out there, Levi, I knew it!" They give a hoot of celebration, "There's so much we can learn from him! I wonder how his anatomy functions? Does he digest bones? What about water?!" 

"Hanji!" Levi growls, annoyed, "I already told you, you're not laying a hand on him. He's not one of your little experiments." 

"I know, I know!" They wave him off. "I won't hurt him, I'm just curious!" 

"I'm holding you to that." 

__

Stirring a bit, Eren gives a sigh. Everything hurts. 

It feels like his muscles are being dragged down by anchors, exhausting his limbs. "Hm..." He murmurs, rolling over. 

He was in water again, that was good. But something was different about this water, something unfamiliar. 

Peeling his eyes open, he takes in the space around him. 

He releases an ear-piercing shriek as he realizes he has absolutely no clue where he is. "Eren?!" Turning to his left, he makes eye contact with a seemingly panicking Levi. 

"Where am I? Why am I not in the water?!" His voice is taught, a suppressed terror cowering beneath it. 

"You passed out," Eren's eyes flicker over to the other, more unfamiliar human, "So we took you here!" They open their arms wide, smiling. 

"Where is 'here'?!" Eren panics, gesturing wildly to the bathtub he's currently stuck in. He couldn't get away even if he wanted to, and that thought terrifies him. 

"The castle?" The human with the hair bun grimaces. 

"On _land_?" The mermaid shrieks, eyes unnaturally wide. "Oh, I'm gonna die here. I'm so gonna die here." 

"You're not gonna die here." Levi insists, crouching beside the tank again. "You have my word." 

Eren drops his head in his hands, "Just eat me or whatever. Get it over with." 

Hanji gapes at him, "Excuse me?" 

Eren looks up, confused, "Aren't you gonna cook me up? Experiment on me?" 

Levi places a hand out to stop him from saying anything further. "Woah, woah, woah---we are _not_ about to eat you. And like I said, there's no way in hell anyone is laying a hand on you." 

The mermaid prince looks up, hope in his eyes, "Do you mean that?"

_Yeah_ , Levi thinks, _he's way too trusting for his own good._

That just meant Levi was gonna have to keep an eye out for him. 

Not that Levi wasn't going to do that anyways. 

"Of course I mean that, Eren." Levi doesn't like the fear that remains ingrained in Eren's features. "Are you hungry? We could get you some food?" 

Eren thinks for a moment, debating on whether or not he's willing to accept food from humans. His stomach suddenly gives a rumble, answering for him. 

"Do you eat fish?" He turns to the person beside Levi, processing their question. He nods. "I knew it!" They cheer, making Eren wince. 

"For fuck's sake, calm down! You're scaring him." Levi grumbles. 

" _'Fuck'_?" Eren's face scrunches up in confusion. He wasn't familiar with English slang. 

Levi jabs a stern finger at Eren, "Don't say that." 

"But you said it?" 

"Yeah, Levi." Hanji turns to Levi, obviously very amused, "You said it?" 

The man stands there with an air of frustration. "Whatever, let's get him some fish." He grabs Hanji's arm, dragging them out of the bathroom with him. The door slams shut behind them, leaving Eren in confusion.


	6. in deep water

**Summary for the Chapter:**

> surprise, surprise...

As soon as Levi and Hanji are out of the room, panic floods through Eren again. 

"Oh, gods...oh, my gods..." He hyperventilates, grasping the edges of the bathtub tightly. "I gotta get out of here. This can't be happening." 

With as much force as he can manage, Eren yanks himself out of the tub and flops onto the tiled flooring. He yelps, the feeling of his tail smacking against the hard floor sending a spike of pain up his front. "Yeah, _ow_." 

After shaking the sensation away, he pulls himself up to the entryway. "What the-" Yeah, Eren had no idea how to work this big slab of wood that blocked his way out. He'd seen Levi grab the metal knob on the side, and what---twist it? 

Can Eren even reach it from the floor? 

Thankfully, the answer was an uneasy yes. It takes a few tries, but eventually, Eren's able to twist the metal piece to swing the cover open. 

He wiggles across the wooden flooring, struggling to get to the next blockade. A trail of water leads behind him, wetting the pathway to the bedroom. 

Just as he reaches for the metal piece on this door too, he hears a muffled voice on the other side, "I'm telling you, Connie, they're hiding something in here!" 

Eren freezes. "Fuck." He curses, having picked the word up from Levi. 

The boy scoots across the room, reaching for anything to cover himself with. His hand grasps a fluffy cover sitting atop some sort of mattress, and he immediately buries himself underneath it. 

The door creaks open, small voices whispering as they wander into the room. 

Eren clutches the key necklace close to his chest, giving small whimpers of fear. He wishes he could just get up and walk away, unhindered by his tail. He wishes he could just wander the land with his own two legs. The key seems to heat up in his palm. 

"Do you hear that?" The voice from outside his fluffy fortress whispers. 

An odd pain spikes through his lower spine, all the way down to the end of his fin. It takes all he has to not cry out. 

Suddenly, the blanket is ripped off him. "What the hell?!" Eren looks up, terrified at the voice of whatever human came to prey on him now. 

"Who's that?!" The bald boy standing beside him shrieks, "And why's he naked?!" 

Then Eren's eyes look down at his tail. 

Wait, scratch that---legs?! 

He wiggles his...toes? His legs feel smooth, just like his fin did before; slick, almost waterproof. A bit of teal colors the sides of his legs, mostly around the outside of his hips and fading all the way down to his ankles. 

"Who are you?" He looks up, remembering the humans in the room with him. 

"Um...Eren?" Eren grimaces, not sure what else to tell them. 

They both stare at him, confused. " _Who?_ " Connie---Eren had learned his name when the other had called it a moment ago---questions incredulously, crossing his arms and leaning forward, "And why the hell are your legs _blue?!_ " 

Eren looks back down at his new legs, just as confused as the other two. His legs weren't _entirely_ blue. Just a little. "Well, why are _yours_ brown?" 

"Huh?!" Connie looks down, gesturing to his pants, "These?" He shares a look with the other guy, "You mean _pants?_ " 

"Uhh..." Eren's eyes bounce between the boys, "Pants?" 

"Alright, who the fuck is this guy?" The other man slaps his hands against his thighs. 

"I don't _know_ , Jean, how the fuck am I supposed to know?" Connie scoffs. 

Jean? Weird name. Why does everyone on land have such weird names? 

"Eren!" Levi's voice booms through the room, startling all three. "What the hell are you two doing in here?!" 

"Levi, who-" 

"None of your fucking business, now leave." The prince growls out. 

Jean sighs, "At least tell us why his legs are blue." 

Hanji's voice erupts over the constant shouting, coming as an odd relief to Eren, "Legs?!" 

They shove past the boys, gasping when their eyes land on Eren's fresh pair of legs. "Eren...?" Levi questions, an eyebrow raised. "How the hell...?" 

Eren only shrugs in response, eyes wide. "Hello?!" Jean shouts, interrupting, "Anyone wanna explain?" 

The mermaid flinches back, a surge of terror hitting him at the loud noise. This, of course, doesn't go unnoticed by a very concerned Levi. "Nope. You two, out. _Now._ " 

__

Levi grabs the two by their trapezius muscles at the crook of their necks, pulling them backwards out of the room. Once outside, "I hate to ask this of you fuckers, because I swore to myself I was never gonna ask you dimwits for anything in my life, but I need you to keep what you just saw between us." 

Jean raises an eyebrow, "And what _is it_ we just saw?" 

"Yeah," Connie starts, crossing his arms, "What's so special about him? You know, besides his weird legs." 

"Just-" Levi takes a stressed breath, pinching the bridge of his nose with his thumb and forefinger, "Do me this one favor?" 

"Gasp!" Jean holds his hand in front of his mouth in a mock gasp, " _Prince Levi_ asking us _peasants_ for _help_?" 

"Guys, come on!" The raven-haired man whisper-shouts, glancing around the hallway. A maid comes walking by, giving Levi a small bow as she passes. He gives her a wave, then continues after she's gone, "Have I ever asked either of you dipwads for anything before?" 

"Alright, alright." Jean sighs, waving him off, "We can keep our mouths shut. But don't be surprised if we get curious." 

"Fine, but if you do, come to _me_. Don't scare Eren any more than you already have." He needed to make sure they wouldn't go to Hanji, either. They sure as hell couldn't keep their mouth closed if their life depended on it. 

With that, Levi walks right back into his bedroom and closes the door. He takes a deep breath, leaning back against the frame. "Eren, are you alright?" 

"Levi, he's got legs!" Hanji cheers, once again scaring the mermaid still sitting on the floor. The blanket, thankfully, is now covering Eren's private parts. "This is amazing! This is proof that mermaids once walked on land with people, Levi! _Proof!_ " Their hands fly wildly through the air in wide gestures. "I wonder if he still swims as fast? It looks like Eren's waterproof film he had on his tail coats his legs too...we'll have to test it!" 

"For holy fuck's sake, shitty glasses, take it down a notch." Levi grumbles, squeezing his eyes shut to suppress an oncoming headache. "Eren, where'd these come from?" He gestures to Eren's new pair of legs stuck out from the blanket. 

"I don't know?" Eren replies innocently, and in Levi's opinion, rather adorably. "They came in here and started yelling, I got so scared Levi-" 

The human prince crouches by Eren, cautiously moving to comfort the mermaid. He gently brushes a hand down his jawline, tilting his chin up to make eye contact with the aquatic boy. "You're okay now. I'm not gonna let anything happen to you, alright?" 

His soft voice, by some surreal manner, manages to calm Eren's racing heart. He nods. 

"You're holding that key..." Hanji starts, apprehensive to interrupt their moment, but still craving answers. She was right, Eren had been holding the key, the metal piece completely encased in his palm throughout the interaction. 

Slowly, Eren eases the death-grip he has on the key, allowing the other two to see it. 

They all gasp. 

Why is it...glowing?!


End file.
